1. Field of the Invention
The present invention relates to an information processing system for collecting, treating, and storing process data including present value, time-series data or historical data, as well as to a processing method for use with such an information processing system.
2. Description of the Related Art
FIG. 13 shows an ordinary system configuration of an information processing system (first related-art example) for collecting, treating, and storing process data. In FIG. 13, a data collection unit 52 collects primary process data gathered or generated by as many as N process control units (data sources) 51-1 through 51-N, at a pre frequency over a network 53. After being treated by the data collection unit 52 for secondary use, the process data is stored into a data preservation unit 54 as secondary process data (application data). Using the secondary process data, a data display unit 55 offers the functions of running business applications and of a man-machine interface.
With such an information processing system having the ordinary system configuration, loads tend to concentrate on the data collection unit 52 because the unit 52 alone collects data, treats the primary process data into secondary process data, and stores the treated data into the data preservation unit 54. If the data collection unit 52 fails for some reason and becomes incapable of performing its processes, the secondary process data may be lost or otherwise become defective, which in turn will prevent the data display unit 55 from providing its display.
Generally, the data collection unit 52 may also carry out processes other than the process data collection at a pre frequency between the process control units 51-1 through 51-N on the one hand and the data display unit 55 on the other hand. For example, the other processes may include: transmission of control commands to the process control units 51-1 through 51-N following their input from the data display unit 55; acquisition of real-time data from the process control units 51-1 through 51-N in keeping with requests from the data display unit 55; periodical treatment of secondary data collected in hourly increments into tertiary process data arranged in daily increments or of secondary data collected in daily increments into tertiary data arranged in monthly increments, and storage of the tertiary process data. In such cases, the loads concentrate on the data collection unit 52 collecting the process data at a pre frequency. This can exhaust the CPU, memory, and other resources of the data collection unit 52 and prevent the unit 52 from doing anything other than the process data collection.
Because the data collection unit 52 alone collects data, treats primary process data into secondary process data, and stores the treated data into the data preservation unit 54, the unit 52 needs to be improved in processing performance. In order to improve its performance, the data collection unit 52 generally needs to be stopped to have its resources (CPU, memory, etc.) reinforced; the performance of the unit 52 cannot be enhanced dynamically while the system as a whole is in operation. In this context, the processing performance is an indicator indicating at which frequency data can be collected from the process control units 51-1 through 51-N, treated, and stored.
That is, so as not to stop the system, the data collection unit 52 needs to incorporate beforehand sufficient resources (CPU, memory, etc.) to provide desired processing performance in the face of a predetermined maximum number of configured process control units as the targets from which to collect data, so that the process control units may be increased in number over time and still dealt with adequately. Thus the data collection unit 52 cannot be adjusted dynamically in performance in keeping with the increasing or decreasing number of target process control units (data sources) configured.
FIG. 14 shows another configuration (second related-art example) in which the technique disclosed in JP-9-34540-A is applied to the above-outlined ordinary system (FIG. 13). This related-art technique involves replicating the data collection unit 62 into individual data collection units 62-1 through 62-M each allocated a predetermined priority in advance. Of all the currently operating data collection units, the one with the highest priority is regarded as a collection master (data collection unit 62-1 in FIG. 14) and the one with the next-highest priority as a collection slave (data collection unit 62-M in the figure), whereby all process data are collected and stored. According to this technique, the currently operating data collection units other than the collection master and collection slave are placed in a standby state. If the collection master or the collection slave fails, another collection master and another collection save are selected according to the priority.
FIG. 15 shows yet another configuration (third related-art example) in which the technique disclosed in JP-2010-198434-A is applied to the above-outlined ordinary system (FIG. 13). This related-art technique involves integrally replicating the data collection unit and data preservation unit into individual data collection units and data preservation units, so that all data collection units may share configuration information 76 about themselves and about the process control units (i.e., nodes) that they target for data collection. According to this technique, the data collection units collect and store data from the targeted process control units (nodes) based on the configuration information 76. Also on the basis of the configuration information 76, the data display unit 75 determines which of the data collection units 72-A and 72-B (with data preservation units 74-A and 74-B) stores necessary secondary process data (application), and sends a query to the applicable data collection unit (data preservation unit).